| Chinese fir is China's fast-growing timber tree species endemic in southern, their soil degradation, productivity reduction has been a major constraint problems of forestry production. With the atmospheric environment is deteriorating, soil acidification has become the important reason to soil degradation and update difficulties of Chinese fir plantation. A serious consequence of soil acidification is aluminum content in soil increased and the the plants were poisoned. In addition, The phenolic acids secreted by the auto-toxicity caused by Chinese fir would be further exacerbated soil acidification, on the one hand, aluminum toxicity on the impact of Chinese fir may be enhanced , on the other hand, A certain concentration phenolic acids may chelate with the aluminum ,then reduce the activity of aluminum thereby reducing the toxicity of plants.In view of this, this paper will base on existing research, use the separated and identified phenolic acids(o-hydroxybenzoic acid) to combine with active aluminum,considering different nutritional conditions,artificial simulate the adversity stress on chinese fir clones by using orthogonal rotary regression of three factors and five levels, and determine some physiological indexes such as relative conductivity, malondialdehyde(MDA) content, superoxide dismutase(SOD) activity and chlorophyll fluorescence kinetics parameters ,etc. Combined the analysis of variance to the index and the factors, the series of the quadratic equation of three factors were optimized and established. At the same time, the interaction between nutritional conditions, phenolic acids and active aluminum will be studied to provide the theoretical and experimental basis for cultivating aluminum-tolerant and phenolic acids-tolerant varieties of Chinese fir , extend and enrich the research of aluminum toxicity to Chinese fir The main results were as follows:To different physiological and biochemical processes of different Chinese fir clones at different stress periods,the significance test on the multiple correlation coefficient of regression model all reached significant level ,which illustrated that the regression equation can fitted actual situation well,and it can ues to reflect the relationship between the experimental factors and different physiological and biochemical processes. So the regression model established under this experimental condition can predict and simulate the changes of different physiological and biochemical processes.1. Effects of combined stress on the relative conductivity of different Chinese fir clones leavesAt different stress periods, the factors that impacted the relative conductivity of different Chinese fir clones leaves are different. To No.01, the nonlinear interaction of nutritional conditions(X32) impacted the relative conductivity at all three stress periods. Besides, the linear interactions of phenolic acids and active aluminum and the interaction between three influencing factors brought different degree effect on the relative conductivity respectively at different stress periods. Among them, the interaction between active Al and nutritional conditions(X1X3) and the interaction between o-hydroxybenzoic acid and nutritional conditions(X2X3) played a significant role at the initial stage of stress, and the influences shown as mutual promotion in higher concentration and mutual antagonistic in lower concentration. At the middle stage of stress, the interaction between active Al and nutritional conditions(X1X3) impacted the relative conductivity in the way of mutual antagonistic in higher concentration and mutual promotion in lower concentration. At the later stage of stress, the interaction between active Al and o-hydroxybenzoic acid(X1X2) had a significant effect on the relative conductivity,and the effect was mutual promotion in higher concentration and mutual antagonistic in lower concentration.To No.11, the factors that impacted the relative conductivity at different stress periods were the linear interactions and the interaction between three influencing factors. Among them, the interaction between active Al and o-hydroxybenzoic acid(X1X2) shown as mutual promotion in higher concentration and mutual antagonistic in lower concentration at the initial stage of stress, and just the opposite at the later stage of stress. The interaction between active Al and nutritional conditions(X1X3) impacted the relative conductivity significantly at the middle stage of stress, and the influences shown as mutual promotion in higher concentration and mutual antagonistic in lower concentration.2. Effects of combined stress on the malondialdehyde(MDA) content of different Chinese fir clones leavesAt different stress periods, the factors that impacted the MDA content of different Chinese fir clones leaves were different. To No.01, at three stress periods, the interaction between active Al and o-hydroxybenzoic acid(X1X2) was all existed to play a significant role to the MDA content. There was a positive correlation between the interaction and the MDA content at the initial stage of stress, but a negative correlation at the middle and later stage of stress. The linear and nonlinear interactions of three influencing factors also had different effects on the MDA content respectively at the different stress periods. Among them, the interaction between active Al and o-hydroxybenzoic acid(X1X2) and the interaction between o-hydroxybenzoic acid and nutritional conditions(X2X3) affected the MDA content significantly at the initial stage of stress, and they both shown as mutual promotion when the material concentration was higher and mutual antagonistic when material concentration was lower. At the middle and later stage of stress, the interaction between active Al and o-hydroxybenzoic acid(X1X2) impacted the MDA content in the way of mutual antagonistic in higher concentration and mutual promotion in lower concentration.To No.11, there were only the linear interactions of active Al and o-hydroxybenzoic acid(X1,X2) that had significantly influence on the MDA content at the initial stage of stress, with the stress time prolonging , the nonlinear interactions of three influencing factors gradually appeared as the factors that impact the MDA content. The interaction between o-hydroxybenzoic acid and nutritional conditions (X2X3) also played a important role to the MDA content at the later stage of stress, which shown as mutual antagonistic when the concentration of o-hydroxybenzoic acid and the level of nutritional conditions were high, and as mutual promotion when the opposite.3. Effects of combined stress on the superoxide dismutase(SOD) activity of different Chinese fir clones leavesThe factors that impact the SOD activity of different Chinese fir clones leaves were not the same at different stress periods. To No.01, the linear interactions of active Al and o-hydroxybenzoic acid(X1,X2)and the interaction between active Al and nutritional conditions(X1X3) impacted the SOD activity significantly both at the initial and later stage of stress. At the middle stage of stress, the factors that impacted the SOD activity were the nonlinear interactions of three influencing factors(X12,X22,X32). The interaction between active Al and nutritional conditions(X1X3) shown as mutual promotion in higher concentration and mutual antagonistic in lower concentration at the initial stage of stress, and shown as the opposite at the later stage of stress. To No.11, the factors that impacted the SOD activity were the nonlinear interactions of active Al and o-hydroxybenzoic acid(X12,X22)both at the initial and middle stage of stress. Including the nonlinear interactions of active Al(X12), the linear interactions and interaction between active Al and o-hydroxybenzoic acid(X1,X2,X1X2) also had significantly influence on the SOD activity. Among them, the interaction between active Al and o-hydroxybenzoic acid(X1X2) shown as mutual antagonistic when the material concentration was higher and mutual promotion when material concentration was lower.4. Effects of combined stress on the initial fluorescence(Fo) of different Chinese fir clones leavesThe main factors that impact the initial fluorescence (Fo) of different Chinese fir clones leaves at different stress periods are not the same. To No.01, the linear interactions of active A(lX1)effected the initial fluorescence(Fo) significantly at all three stress periods. Besides, the nonlinear interactions of active Al, the linear interactions of o-hydroxybenzoic acid and nutritional conditions(X2,X3)and the interaction among three influencing factors brought different degree effect on the initial fluorescence (Fo) respectively at different stress periods. Among them, the interaction between active Al and o-hydroxybenzoic acid(X1X2) and the interaction between o-hydroxybenzoic acid and nutritional conditions(X2X3) significantly affected the initial fluorescence (Fo) separately at the middel and later stage of stress, and they both shown as mutual promotion in higher concentration and mutual antagonistic in lower concentration.To No.11, the factor that impacted the initial fluorescence (Fo) at different stress periods was relatively less, which included the linear and nonlinear interactions of active Al(X1, X12), the linear interactions of o-hydroxybenzoic acid(X2)and the interaction between active Al and nutritional conditions(X1X3). Among them, the interaction between active Al and nutritional conditions(X1X3) impacted the initial fluorescence (Fo) in the way of mutual promotion in higher concentration and mutual antagonistic in lower concentration at the initial stage of stress.5. Effects of combined stress on the photo-chemical efficiency of PSⅡ(Fv/Fm) of different Chinese fir clones leavesAt different stress periods ,the factors that impact the photo-chemical efficiency of PSⅡ(Fv/Fm) of different Chinese fir clones leaves were not the same, but included the the linear interactions of active Al(X1)in both two clones. To No.01, the nonlinear interactions of active Al (X12), the linear interactions of o-hydroxybenzoic acid(X2)and the interaction among three influencing factors influenced the photo-chemical efficiency of PSⅡ(Fv/Fm) respectively at different stress periods. Among them, the interaction between active Al and o-hydroxybenzoic acid(X1X2) played a significant role at the middle stage of stress, and the influences shown as mutual antagonistic in higher concentration and mutual promotion in lower concentration, the interaction between active Al and nutritional conditions(X1X3) played a significant role at the later stage of stress, but the influences shown as mutual promotion in higher concentration and mutual antagonistic in lower concentration.To No.11, the interaction between active Al and o-hydroxybenzoic acid(X1X2) influenced the photo-chemical efficiency of PSⅡ(Fv/Fm) significantly at all three stress periods, and all shown as mutual antagonistic in higher concentration and mutual promotion in lower concentration. An the initial stage of stress, the nonlinear interactions of active Al (X12)also influenced the photo-chemical efficiency of PSⅡ(Fv/Fm). At the middle stage of stress, the nonlinear interactions of three influencing factors all played a important role to the photo-chemical efficiency of PSⅡ(Fv/Fm). 6. Effects of combined stress on the actual photochemical efficiency of PSⅡ(ФPSⅡ) of different Chinese fir clones leavesAt different stress periods ,the factors that impacted the actual photochemical efficiency of PSⅡ(ФPSⅡ) of different Chinese fir clones leaves were not the same. To No.01, the linear interactions of active Al and o-hydroxybenzoic acid(X1,X2)had significant negative correlation with the actual photochemical efficiency of PSⅡ(ФPSⅡ) at three stress periods. The nonlinear interactions of active Al and nutritional conditions(X12,X32)and the interaction between active Al and o-hydroxybenzoic acid(X1X2) brought different degree effect on the actual photochemical efficiency of PSⅡ(ФPSⅡ) respectively at different stress periods. Among them, the interaction between active Al and o-hydroxybenzoic acid(X1X2) impacted the actual photochemical efficiency of PSⅡ(ФPSⅡ) in the way of mutual antagonistic in higher concentration and mutual promotion in lower concentration in the later stage of stress.To No.11, the factors that impacted the actual photochemical efficiency of PSⅡ(ФPSⅡ) at all three stress periods included the linear and nonlinear interactions of active Al(X1, X12).Besides, at different stress periods, the linear interactions of o-hydroxybenzoic acid and nutritional conditions(X2,X3), the nonlinear interactions of o-hydroxybenzoic acid(X22)and the interaction between active Al and o-hydroxybenzoic acid(X1X2) played different roles in the actual photochemical efficiency of PSⅡ(ФPSⅡ). Among them, the interaction between active Al and o-hydroxybenzoic acid(X1X2) impacted theФPSⅡboth at the middle and later stage of stress ,and they both shown as mutual antagonistic when the materials concentration were higher and mutual promotion when the materials concentration were lower at the later stage of stress.
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